This question obviously has a large psychological component, but I think there is a philosophical aspect as well: I have a four year old that is vaguely aware of a death that recently occurred. I do not want him to be afraid that his family will suddenly and permanently vanish, but, as previously discussed on this board, it seems neither moral nor prudent to lie to him. Is there any theory of what happens when someone dies that is at least somewhat plausibly correct but that will not terrify the little guy?

You're right, I think, that this is largely a psychological matter. So I respond here mostly as a fellow parent struggling with precisely this issue. Yesterday, Annabel, the pet goldfish of our our almost four-year old daughter, Lane, died suddenly while Lane was watching . Lane knew immediately what had happened: "Annabel died!" So we weren't confronted with the dilemma of whether to sneak out to a pet store during her nap to buy a fishy-doppelganger. But even though Annabel's death was surprisingly non-traumatic for Lane, it has raised in her all sorts of questions about her dead grandparents (one of whom she knew) and some other deceased pets. We reply that all these people and pets go to the same place. And when she asks where, we say that we don't know. This is border-line misleading, since we're atheists posing as agnostics. (I once replied that they all "went into the ground", but this seemed unnecessarily grim, and not exactly true about Anabel anyway, since she went down the drain.) The...